Unless you live in Calif.,Hawaii, or Alaska, most good Auto Parts stores will come out and scan/read it for you. Apparently we can have a code w/o the check engine light coming on, although I haven't experienced this with the Coupe yet. In addition to checking in here with the gear heads on this Forum like you've done, checking for codes is a good starting point for troubleshooting/diagnosis. As you're hearing here, it could be a few different things.